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Overview
Research in the Victoria Land Coastal Biome affords an excellent opportunity to
study benthic community interactions in relation to gradations in physical, geological,
chemical and biological factors such as sea-ice cover, seabed disturbance by ice scour,
anthropogenic inputs, and planktonic production. A coupled biophysical model of
transport and recruitment dynamics can be developed across the wide latitudinal gradient.
The slow biological pace of Antarctic systems is potentially recorded in sponge spicule
mats and in records created by ice formation. The availability of a long time series of
ecological data and the impending shifts in McMurdo Station contamination levels make
this a singular area for benthic research on disturbance recovery. The intense seasonal
plankton bloom in Antarctica is likely tightly coupled to reproduction and feeding
strategies of the benthos, in a system that is ideal for research on physiological pulsing.
Historical Data
A database on the benthic community structure in McMurdo Sound has been
maintained since 1974 (Oliver 1980, Conlan and Kim unpublished data). Sampling areas
include anthopogenically impacted sites near McMurdo Station, and pristine sites on both
the west and east sides of McMurdo Sound. Impacted sites exhibit chemical
contamination at an abandoned dump site in Winter Quarters Bay, and organic
enrichment near the McMurdo Station sewage outfall (Lenihan et al. 1990, Lenihan 1992,
Lenihan and Oliver 1995). The variety of sites allows assessment of the effects of
different types of pollution on benthic communities in high latitude environments, and
continued studies are timely because of the current installation of a sewage treatment
plant at McMurdo Station. Data from the clean sites on either side of the Sound are
suggestive of the relative importance of larval supply in defining community structures in
this local area (sensu Dayton and Oliver 1977, Barry and Dayton 1988), a hypothesis that
can be tested across a large scale along the Victoria Land Coastal Biome. From the
existing data set, an analysis of long term trends is in progress in collaboration with
Kathleen Conlan at the Canadian Museum of Nature and will be presented at the SCAR
meeting in Amsterdam.
We have well-developed taxonomic expertise for the smaller benthic fauna of
McMurdo Sound that has been complied in a guide by Kathleen Conlan. The guide is
complete with photos that provide a rapid means to identify the often confusing diversity
of animals from the McMurdo vicinity seafloor. This reference will be very useful to any
ecologist studying benthic biodiversity along the Victoria Land coast. We are working
towards integrating our guide with the photographic guide of macrofauna compiled by
Norbert Wu and Peter Brueggeman and available at
http://scilib.ucsd.edu/sio/nsf/fguide/index.html.
Temporal Changes
The time series of benthic data from the McMurdo area is unique. The high value of
the data set can be maintained only by continuity, including in sampling techniques and
taxonomic quality (i.e. Dayton and Oliver 1978). In addition, the installation of a sewage
treatment plant at McMurdo offers an unprecedented opportunity for a large scale
ecological experiment on organic enrichment in a high-latitude polar environment.
McMurdo Station is the largest US base with over 1100 people during the summer
season. The existing outfall is a large point source of organic enrichment (averaging
135,150 liters per day of untreated sewage); the new treatment plant will output a small
fraction of this (pers. comm. F. Brier and B. Coppin). We (Kim and A. E. Murray)
hypothesize that recovery rates following cessation of organic input, an unusual
disturbance, will be much slower than benthic community recovery from typical seasonal
ice-mediated disturbances (Lenihan and Oliver 1995). Through sampling the infauna
over the period in which the sewage treatment facility is implemented, we can track the
recovery of the infaunal community. In addition, we can use recent advances in
molecular technology (e.g. Liu et al. 1997, Osborne et al. 2000) and understanding of the
importance of the microbial biosphere to document recovery rates of this vital community
component following both ice and organic disturbances, in tandem with the recovery of
the infaunal community. The knowledge gained from this research could be applied to
any situation of high organic loading in polar habitats, and would significantly further the
understanding of anthropogenic impacts in polar environments using an integrated
approach to evaluate the recovery of the microbial, microfaunal, and macrofaunal
assemblages after a massive carbon loading perturbation sustained over 10 years.
A longer historical record of benthic community structure can be obtained from
deposited sponge spicules on the seafloor, and in “dirty ice” that contains relict benthic
communities uplifted by anchor ice (Dayton et al. 1969, Bockus 1999) or brought to the
surface by the dynamics of ice movement. Fossil sponge spicules can be dated back to
the Cambrian (Xiping and Knoll 1996, Brasier et al 1997, Zhang and Pratt 2000), and the
thick mat now commonly found on the seafloor in the Antarctic is a record of sponge
communities, though it is unknown how far back in time it extends (but see Leys and
Lauzon 1998). Similarly, the zones of “dirty ice” found near permanent ice shelves
contain intact benthic communities that have been trapped in forming anchor ice and
lifted from the seafloor to the bottom of the ice layer. The gradual ablation of the surface
ice progressively exposes these complete snapshots of the benthos. In areas where
glaciers come into contact, large sections of the seafloor can be ploughed to the surface
(e.g. Bratina Island), providing a record of the deeper benthic community. Though I have
not fully developed the concepts, this approach has great potential for providing a long
record of benthic ecology that can be linked with available pelagic and climatic records.
Spatial Changes
The latitudinal gradient in duration of open water, light intensity/daylight length
(Grebmeier and Barry 1991), and seabed disturbance from ice (sensu Conlan et al. 1998)
should create a gradient in benthic community composition. A straightforward
distributional study recording basic population characteristics that can be correlated with
environmental gradients is a necessary baseline (sensu Clarke and Crame 1992, Clarke
1996). We have formulated a preliminary hypothesis: Suspension feeders are the most
responsive to seasonal productivity peaks, and deposit feeders respond more to total
annual productivity. Active suspension feeders may be the most efficient at utilizing the
intense food pulse, but their high metabolic requirements may not be sustainable through
the rest of the year in areas with short productive seasons. Superimposed on the overall
latitudinal gradient are "pockets" in bays where the ice does not go out as early, giving us
a way of testing the hypothesis beyond simple correlation, though advected production
must also be considered. Stable isotopic analysis of C and N along the Victoria Land
coast (sensu Conlan et al. 2000) may define a gradient in food supply from in situ to
advected sources.
The benthic marine environment in McMurdo Sound is characterized by marked
differences between the biologically rich East Sound and the depauperate West Sound
(Dayton and Oliver 1977). Limited previous observations of currents in the area (Gilmor
et al. 1960, Barry and Dayton 1988, Dunbar and Leventer 1991) lead to the hypothesis
that this pattern is driven by an inflow of oceanic water on the eastern sound, carrying an
abundant supply of larvae, and a return flow of larvae-poor waters from under the
permanent Ross Ice Shelf along the western side of the sound. We (Kim and C. V.
Lewis) propose to investigate this hypothesis using a combination of physical and
biological measurements of the oceanographic system to resolve larval supply and
recruitment timing. A simple coupled biological-physical model (sensu Lewis et al.
1994) will be used to synthesize the results of the initial work, resolve the major
pathways of larval transport and identify areas for future study. This research would lead
to better fundamental understanding of the processes controlling benthic ecosystems
under seasonal and permanent ice cover and produce a basic numerical model of the
regional ecosystem.
Sentinels
Indicator species that respond rapidly to climate conditions must reproduce within the
timespan of the relevant environmental change. In the benthos, this rules out the obvious
large sponges and other long-lived organisms like the urchins and stars. We should focus
instead on the opportunists, such as some of the small polychaetes and amphipods and the
sponge Homaxinella balfourensis (Dayton et al. 1974, Dayton 1989).
Indicator species that provide a long record of growth in skeletal structures (e.g.
scallops, Berkman 1997) provide potential to detect community responses to climate
shifts over a longer time frame. The deeper water gorgonians and corals may offer
sufficient skeletal material to track isotopic changes reflecting environmental shifts
(sensu Dayton 1989, Aharon 1991, Bemis and Geary 1996).
Integration
The Victoria Land Coastal Biome offers a rich educational opportunity to all levels of
students. The surging popularity of tele-teaching (e.g. the Jason project) as well as
smaller scale interactions with local schools and classes via email and pre- and post-field
presentations can reach K-12 levels. Undergraduate students can utilize data and
specimens to complete senior theses or keystone projects. Field courses such as
“Integrative Biology and Adaptation of Antarctic Marine Organisms” target graduate
level students. Interactive exhibits at museum and media sites share progress and
excitement of discovery with the general public. My activity at all these levels ensures
the broadest dissemination of information and offers wide educational opportunities to
students of any age.
Literature Cited
Aharon, P.. 1991. Recorders of reef environment histories: Stable isotopes in corals,
giant clams, and calcareous algae. Coral reefs 10(2):71-90.
Barry, J.P.; Dayton, P.K.. 1988. Current patterns in McMurdo Sound, Antarctica and
their relationship to local biotic communities. Polar Biology 8(5):367-376.
Bemis, B.E.; Geary, D.H.. 1996. The usefulness of bivalve stable isotope profiles as
environmental indicators: Data from the eastern Pacific Ocean and the southern
Caribbean Sea. Palaios 11(4):328-339.
Berkman, P.A.. 1997. Ecological variability in Antarctic coastal environments: past and
present. IN Antarctic Communities: Species, Structure and Survival, Cambridge
University Press, p349-357.
Bockus, D. 1999. Anchor ice disturbance in McMurdo Sound, Antarctica and the
structure of benthic infaunal communities. MS Thesis, CSU Stanislaus/MLML, 54 pp.
Brasier, M.; Green, O.; Shields, G.. 1997. Ediacarian sponge spicule clusters from
southwestern Mongolia and the origins of the Cambrian fauna. Geology 25(4):303306.
Clarke, A.. 1996. Marine benthic populations in Antarctica: patterns and processes. IN
Ross, R.M., E.E. Hofmann and L.B. Quetin (eds), Foundations for ecological research
west of the Antarctic Peninsula, .373-388.
Clarke, A.; Crame, J.A.; et al. 1992. Southern ocean benthic fauna and climate change: a
historical perspective. Royal Society of London. Philosophical transactions. Series B
338(1285:299-309.
Conlan, K. E., G. H. Rau, G. N. A. McFeters, and R. G. Kvitek. 2000. Influence of
McMurdo Station sewage on Antarctic marine benthos: evidence from stable isotopes,
bacteria, and biotic indices. IN Davison, W., C. Howard-Williams, and P. Broady
(eds.), Antarctic Ecosystems: Models for wider ecological understanding, pp 315-318.
New Zealand Natural Sciences, Caxton Press, Christchurch, New Zealand.
Conlan, K.E., Lenihan, H.S., Kvitek, R.G. and Oliver, J.S.. 1998. Ice scour disturbance to
benthic communities in the Canadian high arctic. Marine Ecology Progress Series 166:
1-16.
Dayton, P. K., G. A. Robilliard and A. L. Devries. 1969. Anchor ice formation in
McMurdo Sound, Antarctica and its biological effects. Science 163:273-274.
Dayton, P.K.. 1989. Interdecadal variation in an antarctic sponge and its predators from
oceanographic climate shifts. Science 245(4925):1484-1486.
Dayton, P.K.; Oliver, J.S.. 1977. Antarctic soft-bottom benthos in oligotrophic and
eutrophic environments. Science 197(4435):55-58.
Dayton, P.K.; Oliver, J.S.; et al . 1978. Long-term experimental benthic studies in
McMurdo Sound.. Antarctic journal of the United States 13(4):136-137.
Dayton, P.K.; Robilliard, G.A.; R. T. Paine and L. B. Dayton. 1974. Biological
accommodation in the benthic community at McMurdo Sound, Antarctica. Ecological
Monographs 44(1):105-128.
Dunbar, R.B.; Leventer, A.; et al. 1991. Circulation in eastern McMurdo Sound,
Antarctica, January through November 1990. Antarctic journal of the United States
27(5):117-120.
Gilmour, A.E.; Macdonald, W.J.P.; Van der Hoeven, F.G.. 1960. Ocean currents in
McMurdo Sound. Nature 187(4740):867.
Grebmeier, J.M.; Barry, J.P.; et al. 1991. Influence of oceanographic processes on
pelagic- benthic coupling in polar regions: a benthic perspective. Journal of marine
systems 2(3-4):495-518.
Gutt, J.; Starmans, A.; Dieckmann, G.. 1996. Impact of iceberg scouring on polar
benthic habitats. Marine ecology progress series 137(1-3):311-316.
Lenihan, H. S., Oliver, J. S., Oakden, J. M. and Stephenson, M. A. 1990. Intense and
localized benthic marine pollution at McMurdo Station, Antarctica. Marine Pollution
Bulletin 21(9): 422-430.
Lenihan, H.S.. 1992. Benthic marine pollution around McMurdo station, Antarctica: a
summary of findings. Marine Pollution Bulletin 25(9-12):318-323.
Lenihan, H.S.; Oliver, J.S. 1995. Anthropogenic and natural disturbances to marine
benthic communities in Antarctica. Ecological applications 5(2):311-326.
Lewis, CVW; Davis, CS; Gawarkiewicz, G.. 1994. Wind forced biological-physical
interactions on an isolated offshore bank. DEEP-SEA RES. II 41(1):51-73.
Leys, S.P.; Lauzon, N.R.J.. 1998. Hexactinellid sponge ecology: growth rates and
seasonality in deep water sponges. Journal of Experimental Marine Biology and
Ecology 230(1):111-129.
Liu, W. T., T. L. Marsh, H. Cheng, and L. J. Forney. 1997. Characterization of
microbial diversity by determining terminal restriction fragment length polymorphism
of genes encoding 16S rRNA. Appl. Environ. Microbiol. 63:4516-4522.
Oliver, J. S.. 1980. Processes affecting the organization of marine soft-bottom
communities in Monterey Bay, California and McMurdo Sound Antarctica. PhD
Dissertation, University of California, San Diego.
Osborn, A. M., E. R. B. Moore, and K. N. Timmis. 2000. An evaluation of terminalrestriction fragment length polymorphism (T_RFLP) analysis for the study of
microbial community structure and dynamics. Environ. Microbiol. 2(1):39-50.
Pearse, J.S.; McClintock, J.B.. 1991. Reproduction of Antarctic benthic marine
invertebrates: tempos, modes, and timing. American Zoologist 31(1):65-80.
Xiping, D.; Knoll, A.H.. 1996. Middle and Late Cambrian sponge spicules from Hunan,
China. Journal of Paleontology 70(2):173-184.
Zhang, X-G.; Pratt, B.R.. 2000. A varied middle Ordovician sponge spicule assemblage
from western Newfoundland. Journal of Paleontology 74(3):386-393.